Jacob grass



.l. GRASS.

LITHOGRAPHIC PLATE'FUR OFFSET AND DIRECT PRINTING.

Reissued Feb. 10, 1920.

APPLICATION vFILED IAN- 22. l9|6.

gw'uen l'oz rjgpoz G m:

attorney tlon.

surfaces hitherto provided on the plate,,and afterward, etchin To all whom it may concern land, have invented certain whereby the printing surface,

the metal lithographic .mcos amiss, or roman-Lumen, ENGLAND.

LITHOGRAPHTC PLATE FOR OFFSET AND DIRECT PRINTTNG.

Be it known that I, JACOB GRASS, subject of the German Em eror, residing at 104 New Kings road, ulham, London, Eng-- new and useful Improvements in and Relating to Litho- 1 graphic Plates for Ofi'set and Direct Prmt mg, of which-the following is a spec1fica is to enable the plate to carry more ink than hitherto, thereby impartinga deeper color, to the'print obtained from the plate, elther directly or through the medium of an oflset surface. 7 y In the usual method of providing a metal lithographic plate with a pri-nti surface, the greasy printing surface is app ied to the surface of the plate by means of a transfer,-

obtained in'the well-known'manner, wherei t tlOIlS of the sensltlzed coating of the plate after the surface of the plate surrounding the various portions of the printing surface,- is cleaned from scum by means of a liquid This latter treatment is' called, etching, e1 though not etching in the literal sense. The printingsurface of an ordinary metal lithographic plate consists of a greasy substance on .the surface of the late.

Now according to t e present invention, the printing surface of a metal lithogra hlG plate is etched intaglio into the p ate, consisting of intaglio recesses, can take up and impart more ink, than the mere surface printing lithographic plates.

; The intaglio printing surface is formed on late, by printing photographically throug a positive tpansparency on a sensitized colloid film coating the plate through theexposed and treat film.

,Figure l of thedrawings is an illustration on an enlarged scale of a lithographic R a fl m de. in accordance with vthe in'ven I, tratin g a flat plate of non.

the

. F' i 2 is a greatly magnified section of v F piagmfied section lllusic plate. theiiumeral 1 designates a metal which forms the or- In said dlnary lithographic plate, such as zinc or a a1 ummuni, hav nga groove or depression 2 I first rubbed into the Specification of Reissued Letters Patent. Reissued Feb 10', 1920 Original no. 1,155,352, dated October t, 1915, Serial no. 852,867, filed July 24, reissue filed January 22, 1910. Serial no.

1914.- Application for 73,?40. I I

' therein, constituting an intaglio portion of the plate .which is coated w1th varnish as shown at 3 within said groove, said coating of varnish covering the bottoml of the depression, meral '4 is filled into the groove over the varnish which serves as a mat to hold a maximum quantity of the ink and which extends to the surface" of the plate.

The procem is as follows: A zinc or 51111-- mlnum lithographic plate is coated with a sensitivecolloid film,'such as fish glue sensitized with a bichromate. A positive transparenc rendered suitably opaque, is placed on t e sensitized film. For producmg a. direct printing plate the transparency is placed face downward on the "plate; for

producing an offset printingplate, the transparency 1s 1placed face uppermost and away from the p ate, the transparency being suitably thin.

On exposure to light, the par which are beneath the transparent portions of the-transparency harden. After removal of the transparency,

bath. The usual etchers; recautions in having the etching liquid of t e correct conwhile the ink-designated by the'nuthe plate is washed- -with' water which dissolves away the unhardened portions of the coating of the sistency should be observed. After etching,

the hardened glue or the like. film is softened by diluted hydrochloric acid or other means, and the plate is dried. The inta liO portions ofthe plate can thenbe fille in with lithographic ink, but'to cause the ink to hold better in the recesses and impart a deeper color to the print obtained from the plate a varnish wh ch is not. dissolved b water or grease, such as celluloid varnish, 1s

. 01 int tions of the plate".v Celluloid va i being a mat varnish also provides-aholdfast' for the ink which enters into the pores thereof. The celluloid varnish is rubbed or worked in by means of a cloth and the'ink is thenrolledqinto the vaniishedintaglio The glue or like film'is then washed away by sponging the plate"with"'water." The plate 'is now over with gum-arabic lio poror the like to prevent oxidation, and is then duced by photography,

the varnish o ready for the machine. 3

The positive transparency may by direct impression from a printing surface, such as a half-tone block or set-up type, by type-writing or other suitable manner and rendered, sufliciently opaque dusting over with'a suit; able powder, he positive trans arency can for example be produced by ma 'ng an impression from a printing surface uppn gelatin tracing paper, or. t is medium as the t written matter directly typed thereetching is done) which receptive of water metal surfaces in a etching may etching and, when dampened, non-receptive of lithophic ink. This quahty may be sufliclentl indicated by the words lithographic plate because, all lithographic surfaces have this quality, which is imparted by the known manner. The said etching for two or three minutes is for so short a time that it produces a very shallow intaglio which is ormay perceptible "to sight and touch, and this be otherwise described as a removal of the grain of the surface, which destroys its water-absorbing quality, but said uality remains-on all of the unetched surace of the plate. But the-invention. is not limited to any particularlength of time of or de th of etching so long as the essential resu t is accomplished. v Fig. 2 of. the drawings shows a greatly magnified section of the plate 1, the waterreceptive grain or roughening of which is indicated conventionally) at 5. This grain is removed down to t e solid ungrained body of'the plate or slightl below the bottom of said grain to form t e intaglio'2. 6 is the primary charge of litholgra hic ink applied in the intaglio before t e ardened part of the film is removed. A. dotted line at 4 indicates the impression ink applied when the plate is used for printing. The doc color of the impression produced by plate isprimarily duet/o the intaglio ink-carrying recesses, as distinguished from normal, high and grainedcarrying surfaces hereto case of rpllanographic plates. 7

In 0 er to give a better understanding of the invention by comparison, a portion of a planographic p ate is illustrated in Fig. 3. On this plate the portions of the same which are to be receptive, of lithographic printing ink are made. so receptive by a be prohe transparenc .is then "dustedlover' 15 an o aque pow er, suchas 1n rounding be almost imore used, asn'jnzthe.

greasy ink applied as indicated at 7 on the. top of the gra1n5. In the use of this late the desired quantity of ink is not usual y or always taken u and impressed b the said a parts 7, it is di cult to dampen t e grain 5 in what ma be called the corners 8, which. mark the boundary between the inked parts 7 and the water-receiving parts 5, and consequently there is a tendency for the ink to gradually spread into said corners and en croach upon the parts of the plate which-are intended to receive only water and not ink,

and repeated impressions tend to wear away the design indicated at 7 by, reasonof the eated operations of the damping and 'ng rolls. These difiiculties are increased when the press is run at any but low speeds. In the case of my plate the slight walls sur:-v all lines or dots constituting the design constantly define said lines and dots both inv the reception of ink and in the impre'ssin of same, and protect the designfrom friction and wear, which would otherwise im air it. A common difliculty is that the sur ace of the plate cylinder and of the oilsetting cylinder do not always operate with a perfect rollin action, but on the contrary with some slig t rubbing, because they are not always perfectly'concentric or perfectl cylindrical, and their speeds are not abso utel the same as the speeds of the surfaces whlch contact with them. In the case of my plate there is no friction on the design itself. Consequently the plate herein described will endure to produce clear and uniform impressions throughout any run of impressions which will berequired in practice.

I claim:

1. A method of producing a printing 105 surface on a metal lithographic plate, consisting of coating said plate with a sensitized film, exposing said film to light to the etched recesses of said plate, and filling 116 said recesses, with lithographlc'ink to a plane coincident with the face of the plate, said varnish serving as a mat to holda maximum quantity of ink,-thereby imparting a diseper color to the print Obtained from the 120 P. ate.

2. A method ofproducing a printing surface on a "metal litho raphic late, consisting in coatingv said plate wit a sensis tized colloid film, exposing said film to light through a positive transparency, washing said plate after removal of said transparency, drying said plate, etching said plate, softening said film, after said etching,

drying said plate, applying celluloid varnish i ar- 110 Q ing in coating said 1p ate wit to the etched recesses of said late and filland removin the film. .3. A method producing a rinting surface on a metal litho phic ate, consista sensitized film, exposing said In to light through a transparency, washing said plate after re said moval of the transparenc drying plate, etching said plate, so ning said film after said etching, drying said plate, applying celluloid varnish to the etched recesses of said plate, filling said varnished recesses with said lithographic ink, removing said film by washing around the recesses and g'umming said plate to prevent oxidation.

4 The process of producing an intaglio printing surface on a metal lithographic plate, consistin in coating the same with a sensitive colloi film in the form of a glue, placin a positive transparency on the sensitized 1m rendered suitably opaque, hardening the portions of the sensitized coating of the plate which are locatedpbeneath the trans arent portions of the transparency,"

disso ving away the unhardened portions of the coating of the plate by washing with water, dipping the p ate inla dye bath to render the picture or the like thereon visible, drying the g ate, immersing the same in an etchin bat softening the hardened glue like and removing the same, then drying the plate and filling the intaglio portions of the plate with lithographic ink.

5. The process of .producmg an intaglio printing surface on a metal lithographic 7 plate, consisting in coating the same with a sensitive colloid film in the form of a glue, placing a positive transparency on the sensitized film rendered suitably opaque, hardening the portions of the sensitized coating of the platewhich are located beneath the transparent portions of the transparency, dissolvmg away the unhardened portions ,ef' the coating of the plate by washing with water,:

dipping the late in a dye bath to render the picture or t e like thereon visible, drying the plate, immersing the same in an etching ath, softening the hardened glue like film, removin said film, then drying the plate and wor ing celluloid varnish into the intaglio portions of the plateand then filling said intaglio portions with lithographic ink over the said varnish, whereby the latter being a mat varnish, will cause the ink to enter the pores thereof to produce a deeper color than is otherwise obtainable.

6. A method of producing a printing surface on a metal litho ing in coating said A) ate with a sensitized film, exposing said 1 positive vtransparency, washing said plate after removal of said, transparency, drying said plate, etching said plate, softenin said "film after said etching, drying sai plate filling the etched recesses of the plate with'an ink-Deceptive material, and removing the film. r 7; A method of producing a printing surface on a metal lithog'r'aphlcplate,consisting in'coating said iplate with a sensitized film, exposing said 1m to light through a positive transparency, washing said plate after removal of said transparency, drying said plate, etchin said plate, softening said film after said e hing, drying said plate, fillin grap ic ink and removing the film.

8. A metal lithographic printingsurface having a normal surface which is receptive of water and non-receptive of ink when dampened, portions of said normal surface being removed to form a design or other matter to be lithographically printed.

9. A metal lithographic printing surface having a normal surface which is receptive of water and non-receptive of ink when dampened, and having ink-receiving suraphic plate, consist.

m to light through a the recesses of the plate with lithofaces below said normal surface which lower surfaces form a design or other matter to be lithographically printed.

In testimony whereof I have aflixed my signature hereto. 

